Gable top containers have been widely used in packaging of consumer goods for decades and are familiar to most consumers in the form of the waxed cardboard packaging in which much of the consumer milk and juices are sold. With relatively minor exceptions, the gabled top containers have folded tops which are partially openable with the formation of a dispensing spout. Opposing edges of the walls at the top of the container are sealed closed to each other with an adhesive, thereby forming an upwardly extending ridge which angles out to the container walls.
The standard manner of opening the container comprises pulling a portion of the sealed edges apart, thereby permanently breaking the adhesive bond and permitting pulling out of a folded section to form the spout. Though the spout can be refolded to its original position, the seal remains open, with accessibility of air to the container contents. With contained materials, particularly foods such as milk, which are detrimentally affected by continued exposure to air, failure to completely re-close the container results in substantial loss of shelf life and accelerated spoilage. In addition, the opened seal is susceptible to spillage therethrough, of the container contents, if the container is accidentally tipped or inverted.
Over the years, many closures have been made or suggested for gable top containers, which serve to re-seal the container after the original opening. Some of the closures served the dual purpose of indicating that the container had not been previously opened, in addition to the secondary re-sealing. Closures for gable top containers have almost always been of one of two general types: slide-on closures and container-anchored swivel closures; with the latter requiring separate container engaging and pivoting means.
One of the earliest and simplest of the slide-on closures for gable top containers is disclosed in U.S. Pat. No. 2,336,503, as being a split tube that is cut to size from an extended length of such tubing. In operation, the split section accommodates the upwardly extending portion, or ridge, of the gabled top, when the tube is properly positioned. In a more recent embodiment, in U.S. Pat. No. 3,458,110, various split tube closures are disclosed of configurations including circular, closed rectangular, diamond, triangular, and hexagonal shapes. The closures, in this latter patent, are specifically one-half the length of the container top, in order that they may be moved, by sliding, from the pouring spout area, to the remaining sealed area, without removal of the closure from the container.
Another embodiment of a slidable locking closure is disclosed in U.S. Pat. No. 3,693,864, where the device is described as having a U or V shape, with a closed end; guide means for the sliding engagement; and elements, which cooperate with thickened sections of the container top, to indicate by sight and feel, appropriate positioning.